Richard Brooks, a former tax inspector and author of The Great Tax Robbery

The details emerged after the contents of a huge trove of leaked account files about secret Swiss accounts were published.

Criminal probes in several countries have already been sparked with attempts being made to claw back the cash after the information was taken by a whistle-blowing IT worker in 2007 and passed to French authorities.

The details of 30,000 accounts holding almost £78 billion of assets were revealed after they were obtained by a French newspaper and analysed by a team of investigative journalists.

The documents reportedly include details of almost 7,000 British clients.

They are reported to include evidence that HSBC colluded with some clients to hide accounts from tax authorities in their home countries, according to the BBC.

HSBC reportedly gave one wealthy family a foreign credit card so they could withdraw their undeclared cash at cashpoints overseas.

Richard Brooks, a former tax inspector and author of The Great Tax Robbery, said: "I think they were a tax avoidance and tax evasion service.

"I think that's what they were offering. They knew full well that people come to them to dodge their tax liabilities."

Among those alleged to have been exposed as having accounts with the Swiss arm of HSBC are politicians, sports stars and celebrities as well as criminals and traffickers.

Holding a secret bank account is not illegal, but using one to deliberately conceal assets in order to dodge tax is against the law.

The European Savings Directive, introduced in 2005, was supposed to ensure Swiss banks take any tax owed from undeclared accounts and pass it to the taxman.

However, instead of collecting the money, HSBC reportedly wrote to some customers and offered them ways to circumvent the new tax.

HSBC denies that all the account holders identified were evading tax.

HM Revenue and Customs, which was passed the data in 2010, has clawed back £135 million from some of the 3,600 Britons identified as potentially avoiding tax using the Geneva branch of HSBC

But it has been blasted by MPs over its slow progress and the fact that there has only been one prosecution of an evader to date.

Public Accounts Committee chair, Margaret Hodge MP, said: "I just don't think the tax authorities have been strong enough, assertive enough, brave enough, tough enough in securing for the British taxpayer the monies that are due."

AFP

HSBC said it was 'co-operating with the relevant authorities' over the claims

In a statement the bank said that since the period in question, it had "implemented numerous initiatives designed to prevent its banking services being used to evade taxes or launder money".

It said: "Although there are numerous legitimate reasons to have a Swiss bank account, in some cases individuals took advantage of bank secrecy to hold undeclared accounts.

"This resulted in private banks, including HSBC's Swiss private bank, having a number of clients that may not have fully met their applicable tax obligations

"We have taken significant steps over the past several years to implement reforms and exit clients who did not meet strict new HSBC standards, including those where we had concerns in relation to tax compliance," it added.

"We are fully committed to the exchange of information with relevant authorities and are actively pursuing measures that ensure clients are tax transparent, even in advance of a regulatory or legal requirement to do so.

"We are also co-operating with relevant authorities investigating these matters and we acknowledge and are accountable for past control failures."

Shadow financial secretary to the Treasury Cathy Jamieson said there were "serious questions" for the Chancellor George Osborne to answer about why just one person had been prosecuted in five years and "why the Government's Swiss tax deal has been such an embarrassing flop".

"Tax avoidance and evasion harms every taxpayer in Britain, and undermines public services like the NHS," she said.

But David Gauke, financial secretary to the Treasury, said the Government has recovered more than £130 million from tax-related actions, while prosecutions have also increased significantly.

The Tory MP said: "It clearly is not acceptable for people to evade or aggressively avoid taxes and we have taken a number of measures to address that.